四川丘陵旱地高温季节苜蓿留茬高度的再生效应

Effect of Stubble Height on Alfalfa Regeneration during Hot Seasons in the Arid and Hilly Region of Sichuan Province

明确高温季节苜蓿留茬高度的再生效应,对优化四川丘陵区人工苜蓿草地刈割制度,提高饲草产量具有重要意义。研究表明:(1)7~8月苜蓿留茬高度从0cm增加到5cm,老枝存活率从8.9%增加到72.9%;与留茬高度为0~3cm的处理相比,留茬高度4~5cm处理在30~50cm土层苜蓿根系干重占全部根系干重的百分比增加1~2。(2)7~8月,苜蓿留茬高度从0cm增加到5cm,其新枝萌发高峰期(刈割后8~20d)的单株苜蓿新枝数量增加量从0.35增加到0.50;新枝重量快速增长期(刈割后27~41d)的单株重量增加量从3.09g提高到9.40g。(3)7~8月苜蓿草地留茬高度低于3cm时,全年鲜草产量和当茬产量呈逐年降低趋势;留茬高度高于4cm时,全年鲜草产量和当茬产量在试验期间没有显著降低。四川丘陵区在高温季节(7~8月)适当提高苜蓿留茬高度,有利于提高其安全越夏能力和产量;留茬高度以4~5cm为宜,不宜贴地收获。

To clarify reasonable stubble height is better for not only the optimization of alfalfa slipping system but also the raise of forage yield,therefore it is meaningful to clarify the stubble height for alfalfa at the hilly region of Sichuan province.The results showed that：（1）Survive rate of old branch increased from 8.9%to 72.9%,when the stubble height raised from 0cm to 5cm during July and August;dry weight of alfalfa root in 30-50cm soil increased by 1%-2%for the treatments that stubble height was 4-5cm,comparing with the treatments that stubble height was 0-3cm.（2）At hot seasons（July and August）,with the stubble height raise from 0cm to 5cm,the increased amount of new branch raised from 0.35to0.50,during the peak period（8-20days after clipping）of new branch generation.The increased weight of each branch raised from 3.09 g to 9.40 g,during the rapid development stage（27-41days after clipping）.（3）Yearly forage yield and current rotational forage yield decreased year by year,when stubble height was lower than 3cm in artificial alfalfa land during July and August;while yearly forage yield and current rotational forage yield did not decreased significantly,during the experiments period（2013-2015）,when stubble height was higher than 4cm during July and August.A higher stubble height was better for alfalfa to get a higher capacity to survive over hot period（July to August）and was better for alfalfa to increase forage yield in the hilly region of Sichuan province.4-5cm stubble height was reasonable,but 0cm stubble height is inadvisable for artificial alfalfa land during July and August at the hilly region of Sichuan province.